Lag spikes playing any game

Whenever I play GTA 5 or GTA 5 Online, the game runs perfectly. It’s really smooth, and runs well. A few minutes into the game, I get these lag spikes that last for about 3 to 8 seconds long, and it really makes the game unplayable and it’s really a struggle because I cannot aim, or shoot correctly. In a few seconds it goes away, but repeats itself. It never used to do that. I have tried adjusting my AMD Radeon settings and ingame settings, but I do not know what I am doing half the time, and I really just need a fix. Please help me with whatever I need to do and it will be greatly appreciated.